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Mollusks/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim and Moby walk along a beach. Moby puts his face near a hole in the sand and water squirts from it. Moby holds up a clam he pulled out of the hole. TIM: Yeah, I'm sure it didn't mean anything by that. Tim reads from a typed letter. TIM: Dear Tim and Moby, What's a mollusk? From, Ben. Mollusks are soft-bodied invertebrates, or spineless animals, that have a large, muscular foot and a mantle. MOBY: Beep? TIM: The mantle is a thin layer of skin covering the body. In most mollusks, the mantle produces a material that becomes a hard shell. An animation shows the shell forming on a snail. TIM: Mollusks use their single foot to move around or stick to things. An animation shows a snail in motion. TIM: You can find them on land or in the water; snails, clams, octopuses, squid, and slugs are all mollusks. Images show these mollusks. TIM: Mollusks that live in the water have gills, just like fish. Land-dwelling mollusks breathe air, just like we do. An animation shows a slug breathing. TIM: And some mollusks have a radula, a little row of teeth to break off food. A close-up image shows a radula. TIM: There are over 50,000 species of mollusks. Most of them fit into one of three categories: gastropods, bivalves, and cephalopods. An image shows a snail as an example of a gastropod, a clam as an example of a bivalve, and an octopus as an example of a cephalopod. TIM: Most gastropods, like snails and conches, have a single shell, and all of them move around on their muscular foot, using a secretion of mucus to glide across surfaces. An animation shows a snail moving on the ground. SNAIL: And there ain't nothing I can do about it. MOBY: Beep. TIM: Oh, don't be such a baby. Bivalves, like clams and oysters, have two shells to protect their soft bodies. Both bivalves and gastropods have an open circulatory system. That means they have no veins and arteries, just blood surrounding organs in their bodies. An animation shows an open-shelled clam closing its shell. Then their circulatory system is shown. TIM: Cephalopods, like squids and octopuses, are the most complex mollusks. They have a closed circulatory system, just like ours. And their muscular foot is divided into many tentacles with suckers on them. An animation shows a squid in the ocean. MOBY: Beep? TIM: Yeah, the squid and the octopus have a really cool propulsion system that lets them move quickly through the water. Water between the mantle and the internal organs is squeezed out the back of the animal, pushing it forward like a jet engine. Arrows on the squid show where water enters and exits its body as it swims away. TIM: Many octopuses can change color for camouflage. An animation shows an octopus changing colors and blending into its environment. TIM: And they have highly developed brains, too. An image shows an octopus wearing reading glasses sitting in a chair and reading a book. Tim buries Moby in the sand up to his head. A clam emerges from the sand and squirts water into Moby's face. MOBY: Beep. TIM: Well, maybe I was wrong. Maybe it did mean something by that. Category:BrainPOP Transcripts Category:BrainPOP Science Transcripts